The industrial use of enzymes is often limited by their high cost and rapid inactivation. Soluble enzymes are lost with the product at the conclusion of a process, and must be replenished. One area of technological development involves modification of proteins to enhance their activity and/or stability. Processes, such as those involving site-directed mutagenesis and the cultivation of wild forms of enzymes in extreme environments, i.e. extremophiles, have led to significant advances in enzyme technology involving the reduction in the cost per unit of enzyme activity.
Another means to improve the economic feasibility of enzymes for industrial processes is through enzyme immobilization onto a matrix, which may facilitate re-use of the enzyme. Immobilization research has focused upon means to enhance the transfer of enzymes onto the support, and upon means to ensure that the immobilized enzymes remain active. Inactivation of enzymes during catalytic turnover is, however, a key obstacle which may limit the economic feasibility of enzyme-mediated processes. Enzymes may be inactivated by extremes of temperature, pH, shear, and also by free radicals and other reactive species present in the reaction medium. Immobilization technology has the potential to reduce such enzyme inactivation, and, thus, extend the useful lifespan of the enzymes.
Activated carbon is a well-known absorbent and has been previously used for enzyme immobilization via absorption (A. S. Rani, M. L. M. Das, S. Satyanarayana, J. Mol. Catal. B. Enzymatic, 10, 471, 2000), or following derivatization or cross-linking. It is also frequently used for purification of water, beverages, and other process streams. Activated carbon has been used to remove phenolics and phenolic exudates from cultures of A. Canadensis, to facilitate cell growth (G. M. Roy, Activated Carbon Applications in the Food and Pharmaceutical Industries, Technomic Publishing Co., Lancaster, Pa., 1995). It has also been used for removal of amino acids from protein hydrolysate solutions (Roy, ibid), and for removal of phenolics from soy protein extracts. Activated carbon has also been used to remove chill-sensitive proteins from beer (J. W. Hassler, Purification With Activated Carbon, Chemical Publishing Co., New York, 1974). U.S. Pat. No. 6,582,606 discusses the benefits of activated carbon for microfiltration, in order to reduce fouling of ultrafiltration membranes and enhance separation. However, the prior art is silent as to the effect of activated carbon in enhancing the activity of enzyme solutions.